Unveiling the Bird with Triple Male Traits: How a New Enzyme is Revolutionizing Biology

Males, often referred to as morphs, come in three varieties that vary in look and behavior. The great majority are "independents," which have darker plumage and aggressively defend a tiny territory in leks, or mating arenas, to win over females. Together with an Independent, the somewhat smaller "Satellites," who have lighter-colored plumage, calmly court. By cleverly disguising themselves as females, the more uncommon "Faeder" males are able to enter the mating arenas undetected.

Excess testosterone is detrimental to the Satellites and Faeders, whose tactics aren't predicated on violence. These males have considerably lower blood testosterone levels than Independents, according to previous research.

The genetic components that control testosterone were mostly unknown until recently. Since the three morphs only differ from one another in a "supergene," a DNA area made up of roughly 100 genes, Ruffs can provide insight into this. It began when a chromosomal fragment broke out and then reinserted itself in the other direction approximately four million years ago.

The researchers discovered a gene in the supergene that codes for an enzyme that degrades testosterone while doing gene expression analysis. They discovered that satellites and faeders were producing it in massive quantities.

but not in the testosterone-secreting testes. However, the researchers was taken aback when they discovered that Faeders and Satellites produced far more testosterone in the testes than the Independents. This raised the question of how these two mutants were able to keep their blood testosterone levels low.

The scientists discovered that the Faeders and Satellites have developed a "super enzyme," a very potent enzyme that effectively breaks down testosterone. The blood of Satellites and Faeders had high levels of the super enzyme, but the blood of Independents had none at all. One of the original authors, Alex Zemella, says, "We had assumed that this enzyme plays no role in the blood based on previous research in other animals." However, our findings identified a hitherto unidentified location where the enzyme functions. This implies that the blood can directly control the amount of testosterone in circulation, which was previously disregarded.

This demonstrates the complex tactics that men have developed to improve the effectiveness of their reproduction. "To produce sperm, all males require testosterone in their testes," says main author Jasmine Loveland. However, the hormone also has other consequences. For instance, it can encourage aggressive and courtship behavior in the brain. It's noteworthy to note that the super enzyme appears to be more prevalent in the brains of non-aggressive ruffs, particularly in the hypothalamus. These findings, in addition to the low blood testosterone levels, probably have a significant impact on how they approach mating.

New research avenues are being opened by the finding that variations in a single gene might impact testosterone levels. In the future, the team hopes to further investigate the differences between the sexes and take a closer look at how sophisticated social behaviors are controlled in ruffs.

Reference: “A single gene orchestrates androgen variation underlying male mating morphs in ruffs” by Jasmine L. Loveland, Alex Zemella, Vladimir M. Jovanovi?, Gabriele Möller, Christoph P. Sager, Bárbara Bastos, Kenneth A. Dyar, Leonida Fusani, Manfred Gahr, Lina M. Giraldo-Deck, Wolfgang Goymann, David B. Lank, Janina Tokarz, Katja Nowick and Clemens Küpper, 23 January 2025, Science.